Mechanochemically carboxylated multilayer graphene for Carbon/ABS composites with improved thermal conductivity

Abstract

Dry ball milling of graphite under carbon dioxide pressure affords multilayer-functionalized graphene (MFG) with carboxylic groups as nanofiller for composites of carbon and acrylonitrile- butadiene-styrene copolymers (ABSs). Produced in a single-step process without requiring purification, MFG nanoplatelets are uniformly dispersed in ABS even in the absence of compatibilizers. As compared to few-layer graphene oxide, much larger amounts of MFG are tolerated in ABS melt processing. Unparalleled by other carbon nanofillers and non-functionalized micronized graphite, the addition of 15 wt %MFG simultaneously results in a Young's modulus of 2550MPa (+68%), a thermal conductivity of 0.321W·m-1·K-1 (+200%), and a heat distortion temperature of 99 °C (+9%) with respect to neat ABS, without encountering massive embrittlement and melt-viscosity build-up typical of few-layer graphene oxide. With carbon filler at 5 wt %, the Young's modulus increases with increasing aspect ratio of the carbon filler and is superior to spherical hydroxyl-functionalizedMFG, which forms large agglomerates. BothMFG andmicronized graphite hold promise for designing carbon/ABS compounds with improved thermal management in lightweight engineering applications.